A good deal of attention has been attracted to adoptive immunotherapy with lymphokine activated killer cells (LAK) as highly efficient cancer therapy, which was developed by S. A. Rosenberg et al. Since the study on the mechanism of LAK regulation was recently initiated, the means of enhancing or suppresing LAK activity was hardly studied, although LAK and CTL (cytotoxic T lymphocytes) are considered to participate also in rejection transplanted organs and in autoimmune diseases. Rosenberg et al. recently reported that transforming growth factor-.beta. (TGF.beta.) suppresses generation of LAK and CTL (Cancer Immunol. Immunother., 26, 45, 1988). However, TGF.beta. stimulate the growth of certain tumor cells and it cannot be used as a medicine for human immune diseases.